Field of the Invention
Embodiments of the present invention generally relate to video displays, and more particularly, to a video display providing vision adjustment or manipulation so that multiple users requiring different vision correction can view a common video image without the need for corrective eye glasses.
Background
Cataracts and refractive errors are the principal causes of loss of visual acuity. Vision impairment is pervasive—more than one billion persons in the world need eyeglasses. The number of persons requiring eyeglasses is expected to increase with the increasing use of smartphones and other electronic gadgets that impose heavy near work on the eyes.
Nearsightedness and farsightedness are common refractive problems. It is easy to get the two confused. Nearsightedness generally refers to a condition where an individual can see objects that are near, like a book, much easier than farther away objects, such as a television screen. Farsightedness is the opposite, where an individual can see objects that are far away, but has trouble seeing up closer objects. In both problems, the image is difficult to see because it is not properly focused on the retina. With nearsightedness, the image becomes focused in front of the retina. With farsightedness, the image is focused behind the retina. The shape of a person's eyeballs also can cause refractive problems.
Cataracts are light scattering proteins that opacify the crystallin in certain regions, deforming the eye's point spread function and reducing retinal illumination. Cataracts can be assessed by back scattering or forward scattering. Back scattering reduces visual acuity by decreasing the amount of light reaching the retina while forward scattering adds noise to the retinal image, decreasing contrast.
To date, at least two types of displays have been proposed to implement vision correction for a single viewer or user so that the user need not wear glasses. One such known proposed display uses measurements of refractive errors and cataract maps to allow the viewer to see a displayed image without needing wearable optical corrections when looking at displays. Such known displays may support nearsightedness, farsightedness, astigmatism, presbyopia (reading glasses), coma, keratoconus, other higher-order aberrations and any type of cataracts. According to EyeNetra, knowledge of the eye conditions allows traditional displays go beyond an individual's visual acuity, presenting images that are in focus even without wearing corrective eyeglasses.
Some known proposed system use hardware that is the same as the hardware used in glasses-free 3D displays (dual stack of LCDs), but in higher resolution. These known displays may be used use in daily tasks where using eyeglasses are unfeasible or inconvenient, such as on headmounted displays, e-readers, games, etc.
Some known proposed displays enhance visual acuity by decomposing virtual objects and placing the resulting anisotropic pieces into the subject's focal range. Known displays may be tailored, the tailoring process using aberration and scattering maps to account for refractive errors and cataracts. It splits an object's light field into multiple instances that are each in-focus for a given eye subaperture. Their integration onto the retina leads to a quality improvement of perceived images when observing the display with naked eyes. At least one known proposed display system adapts a light field to compensate for an individual's inability to focus. The known display pre-warps the light field to counter act the distortion on the subject's eyes. It is performed in two main steps: (i) pairing light-field rays and retinal positions to associate a raw intensity to each ray; and (ii) normalizing retinal “pixels”. Given as input an expected image to be received by the retina and wavefront and cataract maps of the subject's eye, the method produces a light field to be shown on a specified display. The known approaches can be described as the projection of depth-dependent anisotropic patterns according to the spatially-distributed optical aberrations of the eye. The depth-dependent patterns are “anisotropic images” virtually placed at the right point in focus for a given optical power in a section for the cornea. Because these images are placed at multiple depths to create a single image in focus, the known system may be described as including a multi-depth feature. The known method attempts to make sure that the depth-dependent patches are seen only through eye sub-apertures with given refractive powers. Light paths that go through opacities or unpredictable scattering sites, such as cataracts, are avoided. The final result is a light field to be displayed at a given distance from the eye.
Acuity enhancement options range from simple eyeglasses to optical replacements and expensive relays for adaptive optics. They are grouped according to the correction bearer. Eyeglasses with simple, bifocal, and multi-focal lenses, contact lenses, LASIK and cataract surgeries can be used to enhance visual acuity. However, all of them require wearing prosthesis or making incisions in the eye. Multi-focus displays and holograms can enhance visual acuity by projecting images on the subject's range of accommodation. These techniques, however, do not account for the subject's individual variability. One proposed display adjusts itself to compensate the subject's eye refractive errors and avoids light scattering materials on the optical path, such as cataracts. The display is to some extent similar to a still-under-research adaptive-optics-based contact lenses, but applied to the device instead of the eye.
A wavelength-dependent tailoring process could create new insights on the eye accommodation behavior for natural scenes when refractive variations among wavelengths are close to null. Convergence-based 3D displays with multi-focus and tailoring features can lead to a new ultra-resolution vision-enhanced 3D technology. At least one known system however does not determine the distance between the display and the eye and does not work for two different users with different prescriptions to view the same display simultaneously without use of glasses.
Another vision correction display is described in U.S. Patent Pub. No. 20110157180 (“Burger”). The virtual vision correction technique described in that patent application provides for the discovery of a user's vision correction needs and can provide vision correction for people with vision problems by making video displayed adapt to a person's vision correction needs. The vision discovery and display adaptation features of the technique can each be employed separately, or can both be employed in concert.
The virtual vision correction technique disclosed in Burger allows users to state their vision prescription needs. Input video is then processed to appear “20/20” to that person when the processed video is displayed. The technique can employ a representative image (such as an eye chart, for example) to determine a user's vision characteristics. Video processing can then be performed once a user's vision characteristics are obtained to adapt input video to be displayed in accordance with a user's vision correction needs.
The virtual vision correction technique in Burger pre-processes an image or video input for display based on the user's vision correction needs by transforming the input image or video. Instead of using additional after-market lenses placed in front of the video glasses, the technique can just change the video displayed. Furthermore, the technique in an “auto-tune” mode can accommodate changes in vision over time, without the need for additional hardware or additional lens purchases, by prompting a user to provide feedback as to the processed video displayed, using user input to further enhance or correct the image/video displayed to the user. However, the Burger application does not disclose a video display that can be adjusted for simultaneous use by multiple viewers having different vision correction needs.
Therefore, there is a need in the art for a vision correction display that can be adjusted for simultaneous use by multiple viewers having different vision correction needs.